Agitator mills of the aforementioned generic type are known for example from DE-GM 90 04 117.8 and DE-A 40 10 926.7.
The static separating arrangement is formed in this case by a screen, preferably a bar screen, which is disposed rotatably or stationary on the outlet side of the grinding chamber. A disadvantage with such constructions is that the screen can become clogged by auxiliary grinding elements or fragments thereof in the course or lengthy operation and moreover when the agitator mill is stopped the suspension of material to be ground (together with auxiliary grinding elements and fragments thereof) can be deposited and dry out on the screen, which in unfavourable cases closes off the openings of the static separating arrangement so that restarting of the agitator mill is precluded before an intensive cleaning or replacement of the screen. In the case of very narrow openings in the static separating arrangement, high pressure values and high flow speeds are also produced in operation, so that fragments of auxiliary grinding elements are pressed into the openings and the operation of the separating arrangement is substantially impaired.
So long as the static separating arrangement is arranged rotatably in the aforementioned known constructions, a sealing gap which is advantageously adjustable in size (cf. for instance FIG. 1 of DE-A 40 10 926.7) is situated between this rotating separating arrangement and the adjacent stationary housing. The width of such a sealing gap is set so narrow that neither auxiliary grinding elements nor material for grinding can pass through.
A dispersing device is also known from DD-A 45 700 in which a conically shaped annular screen, which tapers downwards as far as the suction region of an agitator disc mounted on the agitator shaft, is connected to the agitator shaft. In this case a free annular gap which is two to three times as wide as the diameter of the largest grinding element is provided between the lower end of the screen and the agitator shaft. In operation not only can the suspension flowing back stream through this annular gap but in view of the width of the annular chamber grinding elements, which come into the region of the annular chamber during starting or stopping of the dispersing device, can also pass through the annular gap.
The object of the invention is to construct an agitator mill of the aforementioned generic type in such a way that on the one hand a reliable and trouble-free separation of auxiliary grinding elements and fragments thereof out of the suspension of material to be ground takes place and on the other hand maintenance work, particularly on the static separating arrangement, is greatly reduced.